Optical discs: CD, DVD and Blu-ray

Name:

Date:

Class:

Quick Questions

Shade in the A or B circle for each question.

1. Which optical disc has the smallest storage capacity?

A CD

B Blu-ray

2. Which optical disc type uses a blue-violet laser?

A Blu-ray

B DVD

3. Why can a Blu-ray disc store more data than a DVD?

A Its laser has a shorter wavelength, so pits are packed more closely

B Its laser is brighter, so the pits are made larger

4. Which list shows the discs in order of capacity, smallest to largest?

A DVD, CD, Blu-ray

B CD, DVD, Blu-ray

5. A CD-ROM or DVD-ROM disc is described as:

A Recordable: the user can save new data to it

B Read-only: the data cannot be changed

Match the Pairs

Draw a line connecting each item on the left to its match on the right.

Left column		Right column
1CD (about 700 MB)		AA shorter wavelength packs pits closer together. A longer wavelength would mean pits must be spaced further apart and capacity falls.
2Blu-ray (25 GB or more)		BCD-ROM vs CD-R
3A DVD holds more than a CD because its red laser has a shorter wavelength, so pits are packed closer together		CDVD: red laser, about 4.7 GB
4A read-only disc has data pressed in at the factory, while a recordable disc can have data burned onto it by the user		DThe optical disc with the largest capacity, read by a blue-violet laser
5Blu-ray uses a red laser, so it stores more than a DVD		EBlu-ray uses a blue-violet laser, not a red one. Its shorter wavelength is what lets it pack pits closer and store more.
6A longer laser wavelength packs pits closer, so capacity increases		FThe optical disc with the smallest capacity, read by an infrared laser

Definitions

CD, DVD and Blu-ray

Fill in the Blanks

Complete each line of code by filling in the missing parts.

Blu-ray reads with a ___________ laser

Capacity order: CD < ___ < Blu-ray

CD-___ discs can only be read, not written

A shorter wavelength packs pits ______

Optical discs are read using a _____

Spot the Error

Shade in the letter of the line that contains an error.

Question 1

A disc ← "CD"

B laser ← "infrared"

C capacity ← "25 GB"

Question 2

A disc ← "DVD"

B laser ← "red"

C capacity ← "700 MB"

Question 3

A disc ← "CD"

B laser ← "blue-violet"

C capacity ← "25 GB"

Question 4

A IF disc = "Blu-ray" THEN

B laser ← "red"

C ENDIF

Question 5

A cd ← 700

B dvd ← 4700

C bluray ← 25000

D top ← MIN(cd, dvd, bluray)

Answer Key

Optical discs: CD, DVD and Blu-ray

Section A: Quick Questions

A — CD

A — Blu-ray

A — Its laser has a shorter wavelength, so pits are packed more closely

B — CD, DVD, Blu-ray

B — Read-only: the data cannot be changed

Section B: Match the Pairs

CD (about 700 MB) → The optical disc with the smallest capacity, read by an infrared laser

Blu-ray (25 GB or more) → The optical disc with the largest capacity, read by a blue-violet laser

A DVD holds more than a CD because its red laser has a shorter wavelength, so pits are packed closer together → DVD: red laser, about 4.7 GB

A read-only disc has data pressed in at the factory, while a recordable disc can have data burned onto it by the user → CD-ROM vs CD-R

Blu-ray uses a red laser, so it stores more than a DVD → Blu-ray uses a blue-violet laser, not a red one. Its shorter wavelength is what lets it pack pits closer and store more.

A longer laser wavelength packs pits closer, so capacity increases → A shorter wavelength packs pits closer together. A longer wavelength would mean pits must be spaced further apart and capacity falls.

Section C: Definitions

CD, DVD and Blu-ray — Optical discs read by laser. Capacity rises CD, DVD, Blu-ray as each laser's shorter wavelength packs pits closer. Blu-ray uses blue-violet. Discs are read-only or recordable.

Section D: Fill in the Blanks

Blu-ray reads with a blue-violet laser

Capacity order: CD < DVD < Blu-ray

CD-ROM discs can only be read, not written

A shorter wavelength packs pits closer

Optical discs are read using a laser

Section E: Spot the Error

C — A CD holds about 700 MB. 25 GB is the capacity of a single-layer Blu-ray disc, so the line should be capacity ← "700 MB".

C — A DVD holds about 4.7 GB because its red laser packs pits closer than a CD. 700 MB is the CD capacity, so the line should be capacity ← "4.7 GB".

A — The blue-violet laser and 25 GB capacity belong to a Blu-ray disc, not a CD. The line should be disc ← "Blu-ray".

B — Blu-ray discs are read with a blue-violet laser. A red laser is used for DVDs. The line should be laser ← "blue-violet".

D — The capacities (in MB) rise from CD to DVD to Blu-ray, so the largest is found with MAX. MIN would return the smallest (the CD).